The present invention relates to a write/read apparatus having a rotating recording medium and, in particular, it relates to control of write/read of data stored in the write/read apparatus.
In recent years, it is known to capture passersby and other objects by a surveillance camera placed at a desired position, indoors and outdoors, and record surveillance data such as captured video and sound in a write apparatus in chronological order. The recorded surveillance data is used, for example, for criminal investigation. Typically, media such as a tape and an optical disk are used for recording the surveillance data. In the case of the tape medium, a host system writes and reads the input surveillance data by sequential access. On the other hand, in the case of the optical disk medium, physical block addresses (PBAs) are written on the optical disk in advance and the host system writes the input surveillance data in a sequential or overwrite manner and reads the data randomly by specifying logical block addresses (LBAs).
Further, recently, a write/read apparatus for surveillance data such as a server, a personal computer (PC) and a digital video recorder (DVR) provided with a magnetic disk drive internally or externally becomes in use in order to write and read the surveillance data for a long time with improved image quality and operability. The magnetic disk drive has a general-purpose interface port such as ATA (AT attachment) or SCSI (small computer system interface) and writes and reads the data according to LBA specified by the host system having a file system.
In connection with a technique for writing video data on an optical disk, for example, Japanese Patent Laid-open No. 2002-367341 (Patent Document 1) discloses an information recording medium, a write apparatus and a read apparatus, wherein time map information that associates time information about read operation of recorded video data with LBA is generated and stored as a part of management information for managing the read operation of the video data separately from the video data.
Further, Japanese Patent Laid-open No. 2000-149425 (Patent Document 2) discloses a disk drive, wherein an area for writing system data is separated from an area for writing consecutive data having a constant transfer rate and the consecutive data with the addition of time information is written on a disk-like recording medium in the order of addresses in the area for writing the consecutive data.
Still further, because the surveillance data may be important, it must not be tampered. As a system that prevents tampering of the data in a magnetic disk drive in view of this requirement, Japanese Patent Laid-open No. 2002-133770 (Patent Document 3) discloses an AV information write apparatus that has a first head for data write/read operation and a second head for read operation, which are controlled and driven to input/output the data from/to the outside independently of each other, wherein the AV information apparatus gives sector/track numbers to be written/read to each head and has a buffer for the written/read data.
Further, Japanese Patent Laid-open No. 2002-140171 (Patent Document 4) discloses an information processing system using a magnetic disk drive that has a head with security features for data write/read operation and another write/read head, wherein a PC connected to the head with security features is, in turn, connected to an external network.
Still further, Japanese Patent Laid-open No. 2002-251324 discloses a server system and a security system using a magnetic disk drive that has a switch for physically switching between a write/read mode and a read only mode.